The top leader of al-Qaeda's front group in Iraq has warned that it would target judges and prosecutors, and try to help its prisoners break out of Iraqi jails as a fresh wave of attacks across the country at the beginning of the Muslim holy month of Ramadan killed scores.

A voice message purportedly posted by the Islamic State of Iraq (ISI) leader Abu Bakr al-Baghdadi on various Jihadist Internet forums on Sunday has also called on Sunni tribal leaders to provide support to the fight by encouraging their men to join the terrorist outfit, which is returning to its previous strongholds.

He announced "a new stage of our struggle," and the launch of a plan named 'breaking the walls.'"

"The first priority is releasing Muslim prisoners everywhere, and chasing and eliminating judges and investigators and their guards," according to al-Baghdadi, who replaced Abu Omar al-Baghdadi as ISI leader in May 2010 following the latter's death in a joint U.S.-Iraqi raid.

He also announced the beginning of a war against the United States, and threatened by saying that "you will see them (Qaida militants) at the heart of your country."

Authenticity of the recorded message has not been confirmed. If true, it would be the first online statement from the new leader of al-Qaeda's affiliate in Iraq.

Al-Qaeda in Iraq is regarded by Iraqi officials to be significantly weaker than at the peak of its strength in 2006 and 2007, but Al-Baghdadi's message, which comes seven months after the U.S. pulled its last troops out of the country, is intended to show that it is still capable of spectacular mass-casualty attacks across the country.